Preparation Of Bi₂Te₃-based Thermoelectric Materials

Thermoelectric material is one of the most important functional materials which canbe used to convert thermal energy into electrical energy directly. It is being widely appliedto thermoelectric refrigeration and power generation due to its advantages of no noise,small size, high stability and non-pollution. In the vicinity of room temperature, Bi₂Te₃-based compounds have better thermoelectric performance than other thermoelectricmaterials, so they are widely used in fields of microelectronics, medical military and so on.But the thermoelectric performance of traditional Bi₂Te₃-based bulk materials are still notgood enough and its application is limited. Consequently, how to improve thethermoelectric performance becomes a research hotspot at home and abroad.The p type Bi₂Te₃based bulk materials were prepared by mechanical alloying methodcombined with plasma activated sintering. And then the influences of processparameters（current for activation, current for sintering and sintering temperatures） duringplasma activated sintering process to thermoelectric performance and micro-structure of thematerials were studied. It is found that the thermoelectric performance of materials inparallel pressure direction is much better than that in vertical pressure direction and thepower factor and ZT value of samples sintered at653K can reach4.86×10^-3W-m^-1-K^-2and1.28at room temperature.The n-type Bi₂Te₃based bulk materials were prepared by mechanical alloying andsubsequent hot pressing. Afterwards the influence of amount of Te to thermoelectricperformance of n type Bi2TexSe_0.15alloy was studied, and also amount of Se to n typeBi₂Te₃-xSe_xalloy. The effect of the doping amount of Ag and AgI on the thermoelectricperformance of Bi₂Te_2.85Se_0.15alloy was also investigated. In comparison with thenon-doped samples, the0.2wt%Ag-doped sample obtained an increase of power factorabout15%, and the power factor of the0.2%wt AgI-doped sample increased about10%.